Electroforming apparatus and electroforming method

ABSTRACT

An electroforming apparatus and an electroforming method that are capable of performing high-precision electroforming are provided. An electroforming tank  1  accommodated in an outer tank  2  is continuously supplied with an electrolyte  3  from a control tank  5 , and electroforming is carried out in an overflow layer  10  of electrolyte  3  formed over the electroforming tank  1 . A bus  25  for electroforming that is retained by a retaining jig  30  is carried along the overflow layer  10  by a jig transfer device  20 . The electrolyte  3  overflowing the electroforming tank  1  is collected into a control tank  5  from the outer tank  2  and supplied to the electroforming tank  1  again after being filtered.

TECHNICAL FIELD TO WHICH THE INVENTION PERTAINS

[0001] The present invention relates to an electroforming apparatus andan electroforming method. More particularly, the present inventionrelates to an apparatus and method for producing, by electroforming,tubular members (known as “ferrules”) that may be used in connectorterminal portions for connecting optical fibers or the like.

BACKGROUND OF THE INVENTION

[0002] In connector terminal portions of optical fiber cables, tubularmembers (known as “ferrules”) are used to secure optical fibers, whichare to be connected to each other, coaxially at a predeterminedposition. FIG. 11 shows an example of connection of optical fibers usingsuch ferrules. As illustrated in the figure, optical fibers 202A and202B are inserted into ferrules 201A and 201B, respectively. Theferrules 201A and 201B are fitted into a sleeve 203 and disposed so thatrespective ends of the optical fibers 202A and 202B face each other.

[0003] Ferrules made of ceramics have heretofore been used as thosestated above. However, ceramic ferrules are difficult to machine andcost a great deal to produce. Under these circumstances, a method ofproducing metallic ferrules by electroforming is proposed in thepublications of WO00/31574, WO01/48271, Japanese Patent ApplicationUnexamined Publication (KOKAI) Nos. Sho 59-3859 and Hei 12-162470, etc.In such an electroforming type ferrule producing apparatus, for example,a wire serving as a pattern member for electroforming is placed in anelectrolyte filled in an electroforming tank to perform electroforming.

[0004] Incidentally, connection of optical fibers needs to be made withan extremely high degree of accuracy. Accordingly, ferrules used for theoptical fiber connection require extremely high quality in terms ofdimensions (accuracy in units of micrometers or less is required). Withthe above-described conventional ferrule producing apparatus, however,it is difficult to obtain a uniform electroforming fluid throughout theelectroforming tank even if the electroforming fluid is stirred. Forthis reason, the current density around the wire cannot accurately becontrolled. Consequently, errors occur in the coaxiality of anelectroformed piece formed around the wire (i.e. the coaxiality betweenthe tubular external shape of the electroformed piece and the hollowportion thereof), linearity thereof, the roundness of the sections ofthe external shape and the hollow portion of the electroformed piece,etc. Therefore, the electroformed piece has to be subjected totroublesome fabrication process using a precision machine (e.g. a wirecenterless apparatus). Further, because a retaining member for retainingat least one end of the wire unavoidably needs to be immersed in theelectrolyte, the retaining member undesirably reacts with theelectrolyte to generate impurities. Thus, it is difficult to control theelectrolyte, and the retaining member itself is damaged unfavorably.Furthermore, to effect electroforming of good quality, filtrationcontrol of the electrolyte is indispensable. However, it has heretoforebeen difficult to filter the electrolyte rationally.

[0005] The present invention was made in view of the above-describedproblems, and it is an object of the present invention to provide anelectroforming apparatus and an electroforming method that are capableof satisfactorily performing the electroforming process requiringextremely high accuracy.

[0006] Another object of the present invention is to provide anelectroforming apparatus and an electroforming method that are capableof minimizing the generation of impurities in the electrolyte forelectroforming.

[0007] Still another object of the present invention is to provide anelectroforming apparatus and an electroforming method that are capableof rationally filtering the electrolyte for electroforming.

DISCLOSURE OF THE INVENTION

[0008] An electroforming apparatus according to the present inventionincludes an electroforming tank (e.g. an electroforming tank 1 or 101)having an opening at the top thereof; electrolyte supply means (e.g.supply piping 4, a control tank 5, and a circulating pump 6) forsupplying an electrolyte for electroforming into the electroformingtank; an overflow layer (e.g. an overflow layer 10 or 110) formed overthe opening of the electroforming tank by the electrolyte overflowingfrom the opening; positioning means (e.g. a jig transfer device 20, anda retaining jig 30) for positioning a pattern member (e.g. a bus 25 or125) for electroforming in the overflow layer; a first electrode (e.g.electrodes 36 and 38) connected to the pattern member; a secondelectrode (e.g. an anode electrode 54) provided in the electroformingtank; and a power supply (e.g. a programmable power supply 53) forapplying a voltage between the first and second electrodes. Thus,electroforming is performed in the overflow layer where the condition ofthe electrolyte is substantially uniform throughout (i.e. free fromnonuniformity of the electrolyte composition which would otherwise becaused by impurities). Therefore, it is possible to prevent degradationor variation of the geometric accuracy of the electroformed piece due tononuniformity of the current density in the electrolyte and hencepossible to produce high-precision electroformed pieces in high yield.For example, in the production of a tubular member (e.g. a ferrule 71,72, 181 or 182) for a connector terminal for connecting optical fibersor the like as an electroformed piece, it is possible to markedlyimprove the coaxiality between the external shape of the tubular memberand the hollow portion thereof, linearity of the tubular member, theroundness of the sections of the external shape and the hollow portionof the tubular member, the dimensional accuracy of the outer diameter ofthe tubular member and the inner diameter of the hollow portion, etc.Accordingly, the fabrication process required to increase the accuracyof the tubular member (e.g. the degree of coaxiality, and the outerdiameter) can be reduced to a considerable extent. Consequently,high-precision tubular members (ferrules) can be provided at reducedcosts. Further, because electroforming can be effected as long as thereis a sufficient amount of electrolyte to form an overflow layer, theamount of electroforming fluid required is favorably small.

[0009] Further, in the electroforming apparatus according to the presentinvention, the positioning means has a retaining portion (e.g. busretaining jigs 34A and 34B) for retaining the pattern member. Theretaining portion is provided outside the overflow layer. Thus, theretaining portion is disposed outside the overflow layer, that is,outside the electrolyte. When a wire is used as a pattern member, forexample, both ends of the wire can be retained at both outer sides ofthe overflow layer while a predetermined tension is being applied to thewire. Accordingly, the retaining portion is not immersed in theelectrolyte, and it is therefore possible to prevent the retainingportion from reacting with the electrolyte to generate impurities in theelectrolyte. In addition, there is no possibility of the electrolytebeing carried away to the outside by the retaining portion. Thus, it ispossible to prevent the electrolyte from uselessly disappearing from theelectroforming tank.

[0010] Further, in the electroforming apparatus according to the presentinvention, the first electrode is provided on the retaining portion ofthe positioning means. Thus, the first electrode can be prevented frombeing immersed in the electrolyte. Consequently, the maintenance of theelectrode is facilitated.

[0011] Further, in the electroforming apparatus according to the presentinvention, the positioning means retains a plurality of pattern membersand moves the pattern members sequentially along the overflow layer toperform electroforming. Thus, a plurality of electroformed pieces areformed around the pattern members moving through the overflow layer inthe same way. Therefore, the electroformed pieces are formed under thesame conditions. Accordingly, uniform electroformed pieces can bemass-produced.

[0012] Further, in the electroforming apparatus according to the presentinvention, electrical connection between the first electrode and thepattern members can be ON-OFF controlled for each pattern member. Thus,despite the fact that electroforming is performed simultaneously on aplurality of pattern members, the electroforming process can beappropriately controlled for each individual pattern member.Accordingly, the accuracy of electroforming can be improved, and it ispossible to eliminate variations among a plurality of electroformedpieces thus produced.

[0013] Further, the electroforming apparatus according to the presentinvention includes rotating means (e.g. a driving motor 42) for rotatingthe pattern member about its own axis. Thus, when a tubularelectroformed piece is to be formed around a wire serving as a patternmember, for example, it is possible to perform electroforming uniform inthe circumferential direction. Accordingly, in the production of atubular member for a connector terminal for connecting optical fibers orthe like as an electroformed piece, the degree of coaxiality between theexternal shape of the tubular member and the hollow portion thereof canbe increased markedly.

[0014] Further, the electroforming apparatus according to the presentinvention includes adjusting means (e.g. a horizontal adjuster device11) for adjusting the tilt of the electroforming tank. Thus, asubstantially horizontal overflow layer can be formed over theelectroforming tank by adjusting the tilt of the electroforming tank.Hence, the uniformity of the electrolyte condition in the overflow layercan be improved.

[0015] Further, the electroforming apparatus according to the presentinvention includes collecting means for collecting the electrolyteoverflowing the electroforming tank, and filter means (e.g. a filter 9)for filtering the electrolyte collected by the collecting means. Theelectrolyte supply means supplies the electroforming tank with theelectrolyte filtered through the filter means. Thus, the electrolyte inthe electroforming tank is constantly replaced with a high-purityelectrolyte rationally. In addition, because the electrolyte isrecycled, the electroforming tank need not be replenish with theelectrolyte externally, and the costs can be reduced correspondingly.

[0016] Further, in the electroforming apparatus according to the presentinvention, the collecting means has an outer tank (e.g. an outer tank 2)accommodating the electro-forming tank. Thus, the electrolyteoverflowing the electroforming tank can be collected easily andreliably.

[0017] Further, the electroforming apparatus according to the presentinvention includes shaping means for shaping an electroformed pieceformed around the periphery of the pattern member at an end of theoverflow layer by controlling the flow rate of the electrolyte at theend of the overflow layer. Thus, the electroformed piece can be shapedeasily. The shaping means may have a control plate (e.g. a control plate160) for blocking the flow of the electrolyte.

[0018] Further, in the electroforming apparatus according to the presentinvention, the electroformed piece is shaped into a predeterminedconfiguration by the shaping means, and electroforming is furtherperformed by using the electroformed piece (e.g. a primarilyelectroformed piece 161) as a pattern member. Thus, the configuration ofthe hollow portion of the electroformed piece can be formed easily andaccurately. For example, in the production of a tubular member for aconnector terminal for connecting optical fibers or the like, the hollowportion can be formed with a spot-faced configuration (e.g. a spot-facedportion 181A, 182A or 182B) with high accuracy. Accordingly, aspot-faced configuration or the like can be provided without the need tocarry out fabrication process. Hence, the production cost can bereduced.

[0019] Further, in the electroforming apparatus according to the presentinvention, the electroformed piece formed around the periphery of thepattern member can be separated from the pattern member within theelectrolyte. Thus, the operation (removal operation) of separating theelectroformed piece from the pattern member can be performed smoothly.In other words, when the electroformed piece is separated from thepattern member after the electroformed piece and the pattern member havebeen taken out from the electrolyte, agents or the like attached to theelectroformed piece and the pattern member may become solidified ondrying, which may interfere with the separating operation. When there isa change in volumetric capacity of each of the electroformed piece andthe pattern member due to a temperature change, because theelectroformed piece and the pattern member differ in the coefficient ofthermal expansion, there is dimensional disagreement between theelectroformed piece and the pattern member. Accordingly, it may bedifficult to separate the pattern member and the electroformed piecefrom each other. In contrast, when separation is performed within theelectrolyte, because the environmental conditions where theelectroformed piece and the pattern member are placed are the same asthose during the electroforming process, neither solidification ofagents or the like on drying nor dimensional disagreement between theelectroformed piece and the pattern member will occur. Accordingly, theseparating operation can be conducted smoothly.

[0020] Further, the electroforming apparatus according to the presentinvention includes a reflector (e.g. a reflector 55) provided under thesecond electrode. Thus, the current density produced in the overflowlayer can be appropriately adjusted.

[0021] In an electroforming method according to the present invention,an overflow layer is formed by an electrolyte overflowing anelectroforming tank, and electroforming is performed in the overflowlayer. Thus, because electro-forming is performed in the overflow layerwhere the condition of the electrolyte is uniform throughout, it ispossible to perform high-precision electroforming with high yield. Inaddition, because electroforming can be effected as long as there is asufficient amount of electrolyte to form an overflow layer, the amountof electroforming fluid required is favorably small.

[0022] Further, in the electroforming method according to the presentinvention, a pattern member for electroforming is retained outside theoverflow layer. Thus, a member for retaining the pattern member is notimmersed in the electrolyte, and it is therefore possible to minimizethe generation of impurities in the electrolyte. In addition, there isno possibility of the electrolyte being carried away to the outside bythe member for retaining the pattern member. Thus, it is possible toprevent the electrolyte from uselessly disappearing from theelectroforming tank.

[0023] Further, in the electroforming method according to the presentinvention, a plurality of pattern members for electroforming aresequentially moved along the overflow layer to perform electroforming.Thus, electroformed pieces can be formed around the plurality of patternmembers under the same conditions. Accordingly, uniform electroformedpieces can be mass-produced.

[0024] Further, in the electroforming method according to the presentinvention, the pattern member for electroforming is rotated about itsown axis to perform electroforming. Thus, when a tubular electroformedpiece is to be formed around a wire serving as a pattern member, forexample, it is possible to perform electroforming uniform in thecircumferential direction.

[0025] Further, in the electroforming method according to the presentinvention, the electrolyte overflowing the electroforming tank iscollected, and the collected electrolyte is filtered, and further thefiltered electrolyte is supplied into the electroforming tank to formthe overflow layer. Thus, the electrolyte in the electroforming tank isconstantly replaced with a high-purity electrolyte rationally. Inaddition, because the electrolyte is recycled, the electroforming tankneed not be replenish with the electrolyte externally, and the costs canbe reduced correspondingly.

[0026] Further, in the electroforming method according to the presentinvention, an electroformed piece formed at an end of the overflow layeris shaped by controlling the flow rate of the electrolyte at the end ofthe overflow layer. Thus, the electroformed piece can be shaped easily.

[0027] Further, in the electroforming method according to the presentinvention, the electroformed piece is shaped into a predeterminedconfiguration, and electroforming is further performed by using theelectroformed piece shaped as a pattern member. Thus, the configurationof the hollow portion of the electroformed piece (e.g. a spot-facedconfiguration of the hollow portion of a tubular member for a connectorterminal for connecting optical fibers or the like) can be formed easilyand accurately.

[0028] Further, in the electroforming method according to the presentinvention, the electroformed piece formed around the periphery of thepattern member is separated from the pattern member within theelectrolyte. Thus, the electroformed piece is separated (removed) fromthe pattern member under the same conditions as those during theelectroforming process. Therefore, the removal operation can beconducted smoothly. That is, there is no likelihood that agents or thelike attached to the electroformed piece and the pattern member maybecome solidified on drying, or the dimensions of the electroformedpiece and the pattern member may change owing to a temperature change,as in the case of separating the electroformed piece from the patternmember after the electroformed piece and the pattern member have beentaken out from the electrolyte. Therefore, there is no possibility ofthe separating operation becoming difficult to conduct. Furthermore, theoperation of separating the electroformed piece and the pattern memberfrom each other is executed subsequently to the electroforming process,and there is no need to provide a step for separating the electroformedpiece and the pattern member from each other after the electroformedpiece has been taken out from the electrolyte. Therefore, the number ofsteps required for the production process can be reduced. Hence, costreduction can be achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029]FIG. 1 is a sectional view showing an electroforming apparatus ina first embodiment of the present invention.

[0030]FIG. 2 is a structural view showing the electroforming apparatusin the first embodiment of the present invention.

[0031]FIG. 3 is a perspective view showing a retaining jig.

[0032]FIG. 4 is a perspective view showing the way in which a bus isfitted to an electrode.

[0033]FIG. 5 is a diagram showing the way in which a reflector is placedin an electroforming tank, of which: part (A) shows an arrangement inwhich a concave reflector is placed; and part (B) shows an arrangementin which a convex reflector is placed.

[0034]FIG. 6 is a diagram showing an electroforming procedure.

[0035]FIG. 7 is a sectional view showing examples of ferrules producedby the first embodiment of the present invention.

[0036]FIG. 8 is a diagram showing an electroforming apparatus accordingto a second embodiment of the present invention.

[0037]FIG. 9 is a diagram showing the control of the electrolyte flowrate by a control plate.

[0038]FIG. 10 is a sectional view showing examples of ferrules producedby the second embodiment of the present invention.

[0039]FIG. 11 is a sectional view showing an example of connection ofoptical fibers with ferrules.

PREFERRED MODE FOR CARRYING OUT THE INVENTION

[0040] Embodiments of the present invention will be described below onthe basis of the accompanying drawings.

[0041]FIGS. 1 and 2 show an electroforming apparatus according to afirst embodiment of the present invention.

[0042] As illustrated in the figures, the electroforming apparatus hasan electroforming tank 1 and an outer tank 2 accommodating theelectroforming tank 1. The electroforming tank 1 is a vessel having anopening at the top thereof. The electroforming tank 1 is filled with anelectrolyte (electroforming fluid) 3. Thus, the electrolyte 3overflowing the electroforming tank 1 flows into the outer tank 2. Asthe electrolyte, for example, a nickel sulfamate solution mixed with abrightener and a pit-preventing agent may be used.

[0043] Supply piping 4 is connected to the electroforming tank 1.Through the supply piping 4, the electrolyte 3 is supplied to theelectroforming tank 1 from a supply chamber 5A of a control tank 5 by acirculating pump 6. Meanwhile, discharge piping 7 is connected to theouter tank 2. The electrolyte 3 in the outer tank 2 is collected into acollecting chamber 5B of the control tank 5 through the discharge piping7.

[0044] The supply chamber 5A and the collecting chamber 5B of thecontrol tank 5 are partitioned from each other by an electrolyteisolating plate 5C. The electrolyte 3 containing impurities, which hasbeen collected into the collecting chamber 5B, is supplied to the supplychamber 5A after it has been filtered through a filter 9. Theelectrolyte 3 in the supply chamber 5A is appropriately controlled interms of electrolyte temperature, hydrogen ion concentration, hardness,etc. For example, the electrolyte temperature is adjusted to 50±1° C.The hydrogen ion concentration is adjusted to 4.2±0.2 pH. The hardnessof the electrolyte 3 is appropriately adjusted by controlling the amountof brightener added.

[0045] From the supply chamber 5A, the filtered and appropriatelycontrolled electrolyte 3 is continuously supplied to the electroformingtank 1. As a result, the electrolyte 3 is constantly overflowing theelectroforming tank 1 from the opening 1A at the top thereof. Theelectrolyte 3 above the opening 1A of the electroforming tank 1 (i.e.the electrolyte 3 overflowing the electroforming tank 1) forms anoverflow layer 10. As will be described later, in this electroformingapparatus, electroforming is performed in the overflow layer 10, wherebythe accuracy of electroforming can be increased. The electrolyte 3 usedfor electroforming and containing impurities overflows into the outertank 2 and is collected into the collecting chamber 5B of the controltank 5 and then filtered.

[0046] A horizontal adjuster device 11 is provided under theelectroforming tank 1. The horizontal adjuster device 11 maintains theelectroforming tank 1 in a substantially horizontal position. Thus, asubstantially horizontal overflow layer 10 is formed over the whole areaof the top of the electroforming tank 1, so that the electrolyte isuniformly distributed throughout the overflow layer 10.

[0047] A jig transfer device 20 (not shown in FIG. 1) is provided abovethe electroforming tank 1. The jig transfer device 20 has a pair ofrollers 21 and 22 and a belt 23 passed around the rollers 21 and 22. Thebelt 23 circulates along the longitudinal direction (horizontaldirection in FIG. 2) of the electroforming tank 1.

[0048] A plurality of retaining jigs 30 are secured to the outerperiphery of the belt 23. A bus 25 is loaded onto each retaining jig 30.The bus 25 is a wire serving as a pattern member for electroforming. Itshould be noted that in FIG. 2 the belt 23 is circulatingcounterclockwise, and the operation of loading a bus 25 onto eachretaining jig 30 is carried out at a loading position X.

[0049] As shown in FIGS. 1 and 3, each retaining jig 30 has aplate-shaped base 31 extending in a direction (horizontal direction inFIG. 1) perpendicular to the longitudinal direction of theelectroforming tank 1. The retaining jig 30 further has a pair of sideplates 32A and 32B secured to the base 31 at respective positions nearboth ends of the base 31. The side plates 32A and 32B are arranged tolie just at left and right sides, respectively, of the electroformingtank 1 when the retaining jig 30 is positioned directly above theelectroforming tank 1.

[0050] Bus retaining shafts 34A and 34B are supported by the side plates32A and 32B, respectively, so as to be rotatable about their own axes.Both end portions of a bus 25 are retained by the bus retaining shafts34A and 34B. Thus, the bus 25 is placed in the overflow layer 10overlying the electroforming tank 1.

[0051] More specifically, an electrode 36 is provided on an end of thebus retaining shaft 34A that faces toward the electroforming tank 1. Oneend of the bus 25 is secured to the electrode 36. Meanwhile, a tensiondevice 37 is provided on an end of the bus retaining shaft 34B thatfaces toward the electroforming tank 1. The tension device 37 has anelectrode 38 to which the other end of the bus 25 is secured, and aspring 39. The spring 39 is interposed between the electrode 38 and thedistal end of the bus retaining shaft 34B to apply a predeterminedtension to the bus 25 held between the electrode 36 and the electrode38.

[0052]FIG. 4 shows the details of fitting of the bus 25 to the electrode36. As illustrated in the figure, the bus 25 has an annular hook portion25A formed at an end thereof. The hook portion 25A is engaged with afitting pin 36A of the electrode 36, whereby the bus 25 is fitted to theelectrode 26. It should be noted that fitting of the bus 25 to theelectrode 38 is effected in the same way. Therefore, a descriptionthereof is omitted.

[0053] As shown in FIGS. 1 and 3, a rotating shaft 41 is supported bythe side plates 32A and 32B so as to be rotatable about its own axis.The rotating shaft 41 is driven to rotate by a driving motor 42. Gears43A and 43B are secured to the outer periphery of the rotating shaft 41.The gear 43A is in mesh with a gear 35A secured to the outer peripheryof the bus retaining shaft 34A. The gear 43B is in mesh with a gear 35Bsecured to the outer periphery of the bus retaining shaft 34B. Thus,rotation of the rotating shaft 41 is transmitted to the bus retainingshafts 34A and 34B, thereby allowing the bus 25 retained by the busretaining shafts 34A and 34B to rotate about its own axis. Rotation ofthe bus 25 is controlled to an appropriate value, e.g. 15 rpm or lower,during electroforming. The rotation of the bus 25 allows an improvementin uniformity of the electrolytically deposited metal on the peripheryof the bus 25.

[0054] Electrically conductive electrode rollers 51A and 51B are securedto the bus retaining shafts 34A and 34B, respectively. When theretaining jig 30 is positioned directly above the electroforming tank 1,the electrode rollers 51A and 51B come in contact with electricallyconductive electrode wires 52A and 52B stretched at the left and rightsides of the inner tank 1. Both the electrode wires 52A and 52B areconnected to the minus electrode of a programmable power supply 53.Thus, the electrode rollers 51A and 51B are electrically connected tothe minus electrode of the programmable power supply 53.

[0055] The bus retaining shaft 34A is provided with an electricallyconductive member (e.g. an electric wire, not shown) for electricallyconnecting the electrode roller 51A to the electrode 36. Similarly, thebus retaining shaft 34B is provided with an electrically conductivemember (e.g. an electric wire, not shown) for electrically connectingthe electrode roller 51B to the spring 39 and the electrode 38. Inaddition, the electrically conductive members of the bus retainingshafts 34A and 34B are provided with switching devices (not shown),respectively, so that the electrical connection between the electroderoller 51A and the electrode 36 through the electrically conductivemember and the electrical connection between the electrode roller 51B onthe one hand and the spring 39 and the electrode 38 on the other throughthe electrically conductive member can be ON-OFF controlled by therespective switching devices.

[0056] With the above-described arrangement, the electrodes 36 and 38are electrically connected to the minus electrode of the programmablepower supply 53 to serve as cathode electrodes. The electricalconnection is ON-OFF controlled for each retaining jig 30 by theswitching devices. In other words, voltage application to the buses 25can be ON-OFF controlled for each individual bus 25 in the overflowlayer 10. As a result, electroforming performed on each bus 25 can becontrolled individually.

[0057] On the other hand, as shown in FIGS. 134A, 34B and 2, an anodeelectrode 54 connected to the plus electrode of the programmable powersupply 53 is disposed on the bottom of the electroforming tank 1. Theanode electrode 54 is formed by accommodating metal pellets (e.g. nickelpellets) for electroforming in a mesh-shaped or perforated casing made,for example, of titanium steel.

[0058] The programmable power supply 53 applies a voltage between theanode electrode 54 and the cathode electrodes 36 and 38 so that thecurrent density produced in the overflow layer 10 is maintained at anappropriate value (e.g. 3 to 12 A/dm²; 3 to 4 A/dm² when importance isattached to the degree of roundness of the electroformed piece).Consequently, a metal is electrolytically deposited on the periphery ofthe bus 25, and thus an electroformed piece is formed.

[0059] It should be noted that the electroforming apparatus is providedwith a clamp device, a cut-off machining mechanism for cutting off eachbus 25, and a removal mechanism for removing the bus 25 (see FIG. 6).The clamp device clamps the electroformed piece in the overflow layer10. The clamp device allows the cut-off machining mechanism to cut offthe bus 25 clamped by the clamp device. The bus 25 is removed from theelectroformed piece by the removal mechanism. That is, in thiselectroforming apparatus, the bus 25 and the electroformed piece areseparated from each other in the electroforming fluid 3. Thus,separation of the bus 25 and the electroformed piece will not behindered by a change in volumetric capacity of the bus 25 and theelectroformed piece or by solidification on drying of the agentsattached to the bus 25 and the electroformed piece, which wouldotherwise occur owing to taking out the bus 25 and the electroformedpiece from the electroforming fluid 3. Accordingly, the operation ofremoving the bus 25 can be performed smoothly.

[0060] In addition, as shown in FIGS. 5(A) and 5(B), a reflector 55A or55B may be provided under the anode electrode 54. The reflector 55A or55B is formed from a heat-resistant resin material, for example, toreflect the electric current from the anode electrode 54. Thus, theelectric current is allowed to spread uniformly even into a region inthe electroforming tank 1 where the current density is likely todecrease, whereby the current density distribution in the electroformingtank 1 is made uniform. As a result, the current density produced in theoverflow layer 10 can be controlled appropriately, and it is possible toimprove the uniformity of electrolytic deposition on the bus 25.

[0061]FIG. 5(A) shows an arrangement in which a concave reflector 55A isused. FIG. 5(B) shows an arrangement in which a convex reflector 55B isused. However, the configuration of the reflector may be changed in avariety of ways according to various conditions, e.g. the configurationof the electroforming tank 1, in addition to the illustrated examples.For example, the reflector 55A or 55B may be provided with fine recessesand projections (corrugation).

[0062] Next, the electroforming method carried out by the electroformingapparatus of this embodiment will be described according to FIG. 6. Itshould be noted that in FIG. 6, different positions in the overflowlayer 10 are indicated by 10A to 10G.

[0063] First, at the loading position X of the jig transfer device 20, abus 25 is loaded onto a retaining jig 30. The bus 25 loaded on theretaining jig 30 is fed into the overflow layer 10 by circulation of thebelt 23.

[0064] The bus 25 fed into the overflow layer 10 moves in the overflowlayer 10 successively from 10A to 10G while rotating at a predeterminedrotational speed. In addition, an appropriate voltage is applied betweenthe cathode electrodes 36 and 38 on the one hand and the anode electrode54 on the other so that an appropriate current density is produced inthe overflow layer 10. Consequently, at the positions 10A, 10B and 10C,an electrolytically deposited metal 61 grows on the periphery of the bus25 by electroforming.

[0065] When the outer diameter of the electrolytically deposited metal61 on the periphery of the bus 25 has reached the desired diameter toform an electroformed piece 62, the voltage application to the bus 25 isstopped to suspend the rotation of the bus 25 about its own axis. Then,as shown at the position 10D, the electroformed piece 62 is clamped withthe clamp device (not shown), and a cut position 25B at an end of thebus 25 is subjected to double tapering by machining (e.g. grinding orstamping) with the cut-off machining mechanism. It should be noted thatthe solid black triangular marks in FIG. 6 show that the electroformedpiece 62 is gripped with the clamp device.

[0066] Subsequently, at the position 10E, the bus 25 is pulled away fromthe cut position 25B with the removal mechanism (not shown).Consequently, the bus 25 is cut off at the cut position 25B and pulledout from the electroformed piece 62. At the positions 10F and 10G, theway in which the bus 25 is pulled out from the electroformed piece 62 isshown.

[0067] Upon completion of the formation of an electroformed piece 62 asa tubular member as described above, the electroformed piece 62 is takenout from the overflow layer 10 and subjected to cleaning and drying.Further, according to need, an end of the hollow portion of theelectroformed piece 62 is subjected to spot facing. Thus, a ferrule 71having a spot-faced portion 71A as shown in FIG. 7(A), by way ofexample, is obtained. Alternatively, a ferrule 72 having spot-facedportions 72A and 72B at both ends is obtained.

[0068] As has been stated above, with the electroforming apparatus andelectroforming method according to this embodiment, electroforming iscarried out in the overflow layer 10. Therefore, the current densityaround the bus 25 is stabilized, so that an electroformed piece 62 ofhigh accuracy can be obtained. Accordingly, it is possible to markedlyimprove the ferrule 71 obtained as a result of electroforming in theroundness of the sections of the external shape and the hollow portionand also in the coaxiality between the external shape and the hollowportion of the ferrule 71. In addition, dimensional errors of the outerdiameter of the ferrule 71 and the inner diameter of the hollow portioncan be reduced to extremely small values (e.g. not more than 0.1 μm).Further, because a plurality of electroformed pieces obtained by theelectroforming apparatus are formed around buses 25 moving along theoverflow layer 10, the electroformed pieces can be formed under the sameconditions. Accordingly, it is possible to obtain electroformed piecesof uniform quality. Furthermore, because the voltage application to theplurality of buses 25 can be ON-OFF controlled for each bus 25, thecontrol of electroforming can be effected appropriately for each bus 25.Accordingly, the accuracy of electroforming can be improved remarkably.In addition, because none of the bus (25) retaining portions areimmersed in the electroforming fluid 3, it is possible to minimize theamount of impurities generated in the electrolyte 3. Further, theretaining portions per se can be prevented from becoming deteriorated.Furthermore, because there is no possibility that the electrolyte 3attached to the retaining members will be carried out of theelectrolytic tank 1, the electrolyte 3 will not be lost uselessly. Inaddition, because the cathode electrodes 36 and 38 are not immersed inthe electrolyte 3 either, the maintenance of the electrodes is alsofacilitated. Further, because the electrolyte 3 overflowing theelectrolytic tank 1 is collected into the outer tank 2 and thenfiltered, the electrolyte 3 can be filtered rationally and at low costs.Furthermore, because the electroformed piece 62 and the bus 25 areseparated from each other in the electrolyte 3, the separation can beexecuted smoothly.

[0069]FIG. 8 shows an electroforming apparatus according to a secondembodiment of the present invention.

[0070] As illustrated in the figure, an electroforming tank 101 in thisembodiment has a primary electroforming section 101A and a secondaryelectroforming section 101B, which have different widths. A bus 125 fedinto an overflow layer 110A overlying the primary electroforming section101A of the electroforming tank 101 moves from the primaryelectroforming section 101A with a relatively narrow width toward thesecondary electroforming section 101B with a relatively wide width.

[0071] Control plates 160 are provided at both sides of the primaryelectroforming section 101A. The control plates 160 block theelectrolyte 103 flowing out sideward from the overflow layer 110Aoverlying the primary electroforming section 101A, thereby controllingthe amount of electrolyte 103 applied to the bus 125 at both sides ofthe overflow layer 110A.

[0072]FIG. 9 shows the control of the electrolyte flow rate by thecontrol plates 160 in detail. As illustrated in the figure, each controlplate 160 is placed in a substantially upright position directly abovethe side wall of the primary electroforming section 101A of theelectroforming tank 101 and allowed to move vertically by drive means(not shown) controlled by a controller. In the figure, two differentpositions of the control plate 160 are shown by the solid and chainlines, respectively.

[0073] In this embodiment, electroforming performed on a portion(exposed portion 125C) of the bus 125 extending from each side of theprimary electroforming section 101A is controlled by the verticalmovement of the control plate 160. More specifically, when the controlplate 160 is at a relatively low position as shown by the solid line inthe figure, the flow rate of electrolyte 103 flowing out sideward fromthe overflow layer 110A is controlled. Consequently, the area of aregion of the exposed portion 125C over which the electrolyte 103 flowsis relatively reduced. On the other hand, when the control plate 160 isat a relatively high position as shown by the chain line in the figure,a large amount of electrolyte 103 is allowed to flow out sideward fromthe overflow layer 110A. Consequently, the area of a region of theexposed portion 125C where the electrolyte 103 flows becomes relativelylarge. Thus, the area of a region of the exposed portion 125C where theelectrolyte 103 flows is controlled by the vertical movement of thecontrol plate 160 as stated above, thereby controlling the amount ofelectrolytically deposited metal on the periphery of the exposed portion125C. Consequently, the electroformed piece formed around the peripheryof the exposed portion 125C can be shaped into a desired configuration(e.g. a tapered configuration).

[0074] As shown in FIG. 8, a primarily electroformed piece 161 formed inthe overflow layer 110A overlying the primary electroforming section101A has tapered portions 161A formed at both ends thereof. Theprimarily electroformed piece 161 is once taken out from the electrolyte103 so that an oxide film is formed on the periphery of the primarilyelectroformed piece 161.

[0075] Thereafter, the primarily electroformed piece 161, together withthe bus 125, is fed into an overflow layer 110B overlying the secondaryelectroforming section 101B, where secondary electroforming is carriedout with the primarily electroformed piece 161 and the bus 125 used as apattern member. Thus, a tubular member having a hollow portion patternedon the primarily electroformed piece 161 and the bus 125 is obtained asa secondarily electroformed piece 162. The hollow portion of thesecondarily electroformed piece 162 has highly accurately formedspot-faced portions 162A patterned on the tapered portions 161A of theprimarily electroformed piece 161.

[0076] The secondarily electroformed piece 162 is subjected to cut-offmachining (cutting or grinding) at an approximately central portionthereof with a cut-off machining mechanism (not shown) within theoverflow layer 101B, and the two halves of the secondarily electroformedpiece 162 are pulled out toward both sides with a pulling mechanism (notshown) within the overflow layer 110B. In this way, two ferrules 181each having one spot-faced portion 181A as shown in FIG. 10(A) areobtained. Thus, in this embodiment also, the electroformed piece and thepattern member are separated from each other in the electrolyte.Therefore, the separation can be executed smoothly. Accordingly, theyield of the separating operation (the rate at which the separatingoperation can be effected correctly) increases.

[0077] Although in this embodiment the electroforming apparatus has theprimary electroforming section 101A and the secondary electroformingsection 101B to perform electroforming in two steps, it should be notedthat the present invention is not limited to the described embodiment,and electroforming may be performed in three or more steps. For example,the arrangement may be such that a tertiary electroforming section isprovided next to the secondary electroforming section, and thesecondarily electroformed piece is also shaped with control plates atboth sides of the secondary electroforming section. Then, tertiaryelectroforming is performed on the shaped secondarily electroformedpiece. With this arrangement, the resulting ferrule 182 has spot-facedportions 182A and 182B formed in a two-step structure as shown in FIG.10(B). Similarly, if an (n−1)th-order electroformed piece is subjectedto n th-order electroforming in an n th-order electroforming section, itis possible to form a ferrule having spot-faced portions formed in an(n−1)-step structure.

[0078] As has been stated above, according to this embodiment, aprimarily electroformed piece 161 formed in the primary electroformingsection 110A is used as a pattern member to form a secondarilyelectroformed piece 162 in the secondarily electroforming section 110B.Therefore, a ferrule having a desired configuration (e.g. a spot-facedportion 181A) in a hollow portion thereof can be produced easily andaccurately. In addition, it becomes unnecessary to form a spot-facedportion by fabrication process. Accordingly, the ferrule production costcan be reduced.

1. An electroforming apparatus comprising: an electroforming tank havingan opening at a top thereof; electrolyte supply means for supplying anelectrolyte for electroforming into the electroforming tank; an overflowlayer formed over the opening of said electroforming tank by theelectrolyte overflowing from said opening; positioning means forpositioning a pattern member for electroforming in the overflow layer; afirst electrode connected to said pattern member; a second electrodeprovided in said electroforming tank; and a power supply for applying avoltage between said first electrode and said second electrode.
 2. Anelectroforming apparatus according to claim 1, wherein said positioningmeans has a retaining portion for retaining said pattern member, saidretaining portion being provided outside said overflow layer.
 3. Anelectroforming apparatus according to claim 2, wherein said firstelectrode is provided on the retaining portion of said positioningmeans.
 4. An electroforming apparatus according to claim 1, wherein saidpositioning means retains a plurality of said pattern members and movesthe pattern members sequentially along said overflow layer to performelectroforming.
 5. An electroforming apparatus according to claim 4,wherein electrical connection between said first electrode and saidpattern members can be ON-OFF controlled for each pattern member.
 6. Anelectroforming apparatus according claim 1, further comprising: rotatingmeans for rotating said pattern member about its own axis.
 7. Anelectroforming apparatus according to claim 1, further comprising:adjusting means for adjusting a tilt of said electroforming tank.
 8. Anelectroforming apparatus according to claim 1, further comprising:collecting means for collecting the electrolyte overflowing saidelectroforming tank and filter means for filtering the electrolytecollected by said collecting means; wherein said electrolyte supplymeans supplies said electroforming tank with the electrolyte filteredthrough said filter means.
 9. An electroforming apparatus according toclaim 8, wherein said collecting means has an outer tank accommodatingsaid electroforming tank.
 10. An electroforming apparatus according toclaim 1, further comprising: shaping means for shaping an electroformedpiece formed around a periphery of the pattern member at an end of saidoverflow layer by controlling a flow rate of the electrolyte at the endof said overflow layer.
 11. An electroforming apparatus according toclaim 10, wherein said shaping means has a control plate for blockingflow of said electrolyte.
 12. An electroforming apparatus according toclaim 10, wherein the electroformed piece is shaped into a predeterminedconfiguration by said shaping means, and electroforming is furtherperformed by using said electroformed piece as a pattern member.
 13. Anelectroforming apparatus according to claim 1, wherein the electroformedpiece formed around the periphery of said pattern member can beseparated from said pattern member within the electrolyte.
 14. Anelectroforming apparatus according to claim 1, further comprising: areflector provided under said second electrode.
 15. An electroformedpiece formed by the electroforming apparatus according to claim
 1. 16. Atubular member for an optical fiber connector terminal, said tubularmember being formed by the electroforming apparatus according toclaim
 1. 17. An electroforming method wherein an overflow layer isformed by an electrolyte overflowing an electroforming tank, andelectroforming is performed in the overflow layer.
 18. An electroformingapparatus according to claim 17, wherein a pattern member forelectroforming is retained outside said overflow layer.
 19. Anelectroforming method according to claim 17, wherein a plurality ofpattern members for electroforming are sequentially moved along saidoverflow layer to perform electroforming.
 20. An electroforming methodaccording to claim 17, wherein the pattern member for electroforming isrotated about its own axis to perform electroforming.
 21. Anelectroforming method according to claim 17, wherein the electrolyteoverflowing said electroforming tank is collected, and the electrolytecollected is filtered, and further the electrolyte filtered is suppliedinto said electroforming tank to form said overflow layer.
 22. Anelectroforming method according to claim 17, wherein an electroformedpiece formed at an end of said overflow layer is shaped by controlling aflow rate of the electrolyte at the end of said overflow layer.
 23. Anelectroforming method according to claim 22, wherein the electroformedpiece is shaped into a predetermined configuration, and electroformingis further performed by using the electroformed piece shaped as apattern member.
 24. An electroforming method according to claim 17,wherein the electroformed piece formed around a periphery of the patternmember is separated from said pattern member within the electrolyte. 25.An electroformed piece formed by the electroforming method according toclaim
 17. 26. A tubular member for an optical fiber connector terminal,said tubular member being formed by the electroforming method accordingto claim 17.